Neuro 1 Flashcards
integrative components of nervous system
-receive, store, and process sensory information
-orchestrate the appropriate motor responses
nervous system
-divided into:
-CNS- brain stem and spinal cord
-PNS- sensory receptors, sensory nerves, and ganglia outside the CNS
mid brain
reflex
hypothalamus
-homeostasis
-ventral to thalamus
-regulate body temperature, food intake, water balance
-also an endocrine gland
-controls hormone secretion of pituitary gland
-secretes releasing hormones and release inhibiting hormones into hypophysial portal blood -> release of inhibition of anterior pituitary hormones
-contains cell bodies of neurons of the posterior pituitary gland that secrete antidiuretic hormone (ADH) and oxytocin
pituitary
hormone guide
sensory/afferent division
-visual, auditory, chemoreceptors, and somatosensory (touch) receptors
-transmitted to higher levels of nervous system and finally cerebral cortex
huntington and parkinson cases
-test
motor/efferent divison
-carries information out of nervous system
-contraction by secretion of endocrine and exocrine glands
-
mechanoreceptors
-tactile
-touch
-feeling indentations
-vibration
-B12 deficiency, poor circulation- neuralgia
brain stem
-medulla
-pons
-midbrain
-10/12 CN- carry sensory information to brain stem and motor information away
diencephalon
-thalamus
-hypothalamus
-between brain- between cerebral hemispheres and brain stem
cerebral hemisphere
-cerebral cortex
-white matter
-basal ganglia
-hippocampal formation
-amygdala
spinal cord
-most caudal portion of CNS
-base of skull to first lumbar
-31 pairs of spinal nerves- sensory and motor
-sensory carries input to spinal cord
-motor carries information from spinal cord
-ascending- carries up
-descending- carry down
medulla
-rostral extension of spinal cord
-contains autonomic centers -> regulate breathing and blood pressure
-coordinate swallowing, coughing, vomiting
pons
-rostral to medulla
-balance, posture, breathing
-relays information from cerebral hemispheres to the cerebellum
midbrain
-rostral to pons
-control eye movements
-contains relay nuclei of auditory and visual systems
cerebellum
-foliated (leafy) structure
-attached to brain stem
-between cerebral cortex and spinal cord -> integrates sensory information about position from spinal cord, motor information from cerebral cortex, and information about balance form vestibular organs of inner ear
-dorsal to pons and medulla
-coordination of movement
-planning and execution of movement
-posture
-coordination of head and eye movement
thalamus
-processes almost all sensory information going TO the cerebral cortex
-processes almost all motor information coming FROM cerebral cortex to the brain stem and spinal cord
brocas area
-
cerebral hemispheres
-consist of cerebral cortex, underlying white matter, 3 deep nuclei (basal ganglia, hippocampus. amygdala)
-perception, higher motor functions, cognition, memory, emotion
cerebral cortex
-convoluted surface of cerebral hemispheres and consists of 4 lobes:
-frontal, parietal, temporal, occipital
-lobes are separated by sulci or grooves
-receives and processes sensory information and integrates motor functions
-sensory and motor- primary, secondary, tertiary > depends on how directly they deal with sensory or motor processing
-primary- direct and involve fewest synapses
-tertiary- require most complex process and have greatest # synapses
-limbic association area involved in motivation, memory, emotions
macula
-highest density of rods -> sensory input
-macular degeneration
-loose central vision
-directly in front is blurry and background is fine vision
-central vision loss- cloudy / black
primary motor/sensory cortex
-motor- contains upper motoneurons- project directly to spinal cord and activate lower motoneurons that innervate skeletal muscles
-sensory- contain primary visual cortex, auditory, somatosensory, and receive information form sensory receptor sin the periphery with only few intervening synapses
secondary and tertiary sensory/motor cortex
-surround primary areas
-involved with more complex processing by connecting association areas
3 deep nuclei of cerebral hemispheres
-basal ganglia- contain caudate nucleus, putamen, globus pallidus -> receive input from all lobes of cortex and have projections, via the thalamus, to frontal cortex to assist in regulating movement
-hippocampus- involved in memory
-amygdala- involved with emotions and communicates with ANS via hypothalamus (effect emotions on heart rate, pupil size, hypothalamic hormone secretion)
-hippocampus + amygdala = limbic system
structure of neuron
-cell body (soma) surrounds nucleus- contains ER, golgi -> protein synthesis
-dendrites- receive information and contain receptors for neurotransmitters that are released from adjacent neurons
-axon hillock- axon projects from here -> specialized region which ajoins spike initiation zone (initial segment) where action potentials are generated to send information
-dendrites are numerous and short -> axons only 1
-cytoplasm of axon- dense, parallel arrays of microtubules and microfilament rapidly move material between cell body and axon terminus
-axon terminates on target cells
-NMJ- neuron to skeletal muscle
glial cells
-over half of brains volume
-function as support cells for neurons
-properties of stem cells and give rise to new glial cells or new neurons in adults
-astrocytes- supply metabolic fuel as lactic acid to neurons, also synthesize neurotransmitters, secrete trophic factors, that promote neuronal survival, module cerebral blood flow, help maintain brains extracellular K concentration
-oligodendrocytes- synthesize myelin in CNS (schwann synthesis myelin in PNS)
-microglial- proliferate following neuronal injury and scavenge to remove cellular debris
synaptic relays
-synapses in relay nuclei integrate converge information
-relay nuclei are throughout CNS but especially thalamus
-relay nuclei have several different types of neurons -> interneurons and projection neurons
-projection neurons extend long axons out of nuclei to synapse in other relay nuclei or in cerebral cortex
-almost all information going to and coming from cerebral cortex is processed in thalamic relay nuclei
topographic organization
-sensory and motor is encoded in neural maps
-somatosensory system-> somatotopic map formed by array of neurons that receive information FROM and send information TO specific locations on the body
-preserved at each level of nervous system (even cerebral cortex)
-visual system-> topographic representation is retinotopic
-auditory system- tonotopic
decussations
-almost all sensory and motor pathway is symmetric
-information crosses from one side (ipsilateral) to the other (contralateral) side of brain and spinal cord
-sensory on one side is relayed to contralateral cerebral hemisphere (vice versa)
-some pathways cross in spinal cord (pain) and may cross in brain stem
-crossing are decussation
-commissures- areas of brain that contain only decussating axons
-ex. corpus callosum is commissure connecting the 2 cerebral hemispheres
-visual system- half of axons from each retina cross to contralateral side and half remain ipsilateral
-visual fibers cross in optic chiasm
nerve fibers classification
-classified according to conduction velocity
-conduction velocity depends on size of fibers and presence or absence of myelination
-larger the fiber higher the conduction velocity
-increased myelin increase conduction velocity
-large myelinated fibers- fast
sensory pathways
-receptors are specialized epithelial cells
-somatosensory and olfactory- receptors are 1st order or primary afferent neurons
-convert stimulus ( sound waves, electromagnetic waves, pressure) into electrochemical energy -> sensory transduction
-sensory transduction mediated through opening or closing specific ion channels
-receptor potential- change in membrane potential of sensory receptor
-after transduction and generation of receptor potential -> info transmitted to CNS along sensory afferent neurons (designated first order, second order, third order, fourth order neurons
-first order- closest to sensory neurons
-high order neurons- closer to CNS
A 63-year-old man is brought to his primary care PA because of
concern on the part of his family that he is acting differently. He has been having a worsening tremor at rest and difficulty walking. His family states that when he walks, he often has difficulty stopping. He has no personal or family medical history. On examination, he has a mask-like facial expression with little blinking. He is noted to have a fine tremor at rest in a “pill-rolling” manner. He has muscular rigidity and a stooped posture. On walking, the patient is noted to have rapid propulsion forward with an inability to stop. He shows no signs of dementia or depression. He subsequently is diagnosed with Parkinson disease
-stooped posture, back rigidty, masked face, flexed elbows and wrists, tremors in the legs, forward tilt of trunk, reduced arm swing, hand tremor, slightly flexed hip and knees, shuffling, short, stepped gait
-direct pathway inhibitory reaction tells muscles to remain still normally- parkinsons lack that
-basal ganglia located near thalamus in the diencephalon
-basal ganglia receive synaptic input from motor cortex (as well as from sensory association and
prefrontal cortex) -> send output to thalamus -> feeds back to the cortex
-connections from and back to motor cortical areas -> basal ganglia provide motor loop that contributes to the planning and
programming of voluntary movement
-basal ganglia important for some cognitive
processes-> organization of behavioral responses and verbal problem solving
-4 nuclei of the basal ganglia-
striatum, globus pallidus, substantia nigra, and subthalamic nucleus.
-the motor loop comprises 2 parallel pathways that travel from the cortex through
the basal ganglia -> to thalamus
-> back to cortex.
-In direct pathway, excitatory input to basal ganglia excites thalamic neurons by inhibiting inhibitory output neurons in
internal segment of the globus pallidus.
-indirect pathway- excitatory input to basal ganglia further inhibits thalamic neurons by disinhibiting the inhibitory output neurons in the internal segment of the globus pallidus.
parkinsons: dopamine
-dopamine release from pars compacta neurons in the
substantia nigra -> excites direct pathway (by D1
receptors) -> which inhibits the inhibitor output neurons-> increasing thalamic activity -> increase movements initiated in the cortex
-whereas dopamine simultaneously inhibits the indirect pathway (by D2 receptors), further increasing the inhibition of the inhibitory output neurons.
-Loss of dopaminergic neurons in Parkinson disease reduces the activation of the direct pathway and the inhibition of the indirect pathway -> allow greater
inhibition of thalamic neurons and greater suppression
of movements initiated in the cortex -> hypokinetic signs of this disease
lesions of optic nerve optic chiasm and optic tract
test
A 65-year-old man presents to his primary care PA complaining of difficulties with his vision, particularly at night. The blurred vision is primarily in the right and left peripheral fields. He has myopia and wears corrective lenses. The physical examination reveals visual acuity of 20/100 (needs to be 20ft away when he should be at 100) bilaterally with visual field deficits on the right and left periphery.
-physical examination of eye neglected -> can identify and localize many disease
-Tumors or ischemic events may affect nerve tracts including the optic nerve tract
-location of the lesion -> predictable visual change
based on optic tract.
-Lesions of optic chiasm affect both of the peripheral visual fields -> spare midline visual fields
-ex. pituitary tumor that compresses the optic chiasm
-lesion in an optic nerve will
result in blindness in ipsilateral eye
-lesion in optic tract -> homonymous hemianopia
-pupil size and retinal changes reflect underlying medical conditions.
fovea
Region of the retina, in line with the visual axis, which has become specialized
for high-acuity vision by the radial displacement of blood vessels and all cell layers that
can interfere with light reaching the outer segments of the cone photoreceptors that
are concentrated there
rods
Low-acuity, achromatic photoreceptors having long outer segments that are
specialized for high sensitivity in dim light
cones
High-acuity, chromatic photoreceptors having short outer segments that are
specialized for high temporal, spatial, and chromatic resolution in bright light.
saccades
Quick, preprogrammed, ballistic eye movements used in searching for
visual targets (contrasted with smooth pursuit movements that track already engaged
targets).
first order neuron
-primary sensory afferent neuron
-in somatosensory and olfaction its also the receptor cell
-when the sensory receptor is specialized epithelial cell -> it synapses on first order neuron
-when receptor is also primary afferent neuron there is no need for synapse
-usually has its cell body in dorsal root or spinal cord ganglion -> exceptions: auditory, olfactory, visual
-synapse on second order neurons in relay nuclei (located in spinal cord or in brain stem)
-many synapse on single second order neuron within relay nucleus
interneurons
-in relay nuclei -> can be inhibitory or excitable
-process and modify sensory information received from first order neurons
-axons on second order neurons leave the relay nucleus and ascend to the next relay located in the thalamus where they synapse on 3rd order neurons
-on the way to the thalamus the axons on these second order neurons cross at midline
-decussation (crossing) may occur in spinal cord or in brain stem
third order neurons
-reside in nuclei in thalamus
-second order neurons synapse on single third order neuron
-relay nuclei process information they receive via local interneurons (Inhibitory or excitatory)
fourth order neurons
-reside in appropriate sensory area of cerebral cortex
-there are secondary and tertiary areas, as well as association areas in cortex -> All integrate complex sensory information
